Won't Start. Bad o2 Sensor?

[REIMER]

Hello,

Just saying hello, this is my first post and I'm new to the E30 platform. I drove VW before but I love the E30! :D Don't go to hard on me because I don't know much and hopefully I am posting this in the right place.

I just replaced the clutch on my 85 325e, and it ran perfectly no problems. The problem is I didn't secure the o2 sensor very well and it got unplugged when I hit a massive bump here in Colorado.

The car started to sputter and I barley got it home. I put a new o2 sensor in it and now all it does is crank. I unplugged the battery for a possible reset and it hasn't worked. I believe it's getting fuel and spark.

Please help I have no clue what happened. Thanks!

[MR 325]

A bad (or missing) o2 sensor will not keep your car from starting. Not likely to be the problem.

Did you reinstall the crank sensors in the trans securely?

[REIMER]

I believe did correctly, because drove the car for about 3 weeks after I did the clutch. The thing is it didn't start after the o2 sensor fell out so I guess that could be a coincidence?

[jlevie]

That would be a coincidence. The engine will start and run without the O2 sensor.

At this point there is no clue as to what the problem is. The first check would be for spark when cranking. The next check (if there is spark) would be to see if fuel rail pressure is correct when cranking.

[Andy.B]

Did the o2 sensor fall out of the exhaust bung? Or did it simply become unplugged. I am confused as to how an o2 sensor falls out.

[Andy.B]

I would confirm that you are getting spark, and check to see if the injectors are firing (which could easily be done by feel or by ear... Eta injectors are noisy).

It you have fuel and spark, then you have to start looking at compression, timing, bad coolant temp sensor, bad AFM, intake leaks, or incorrect fuel pressure. O2 sensor only effects trim a small amount of the time on the eta engines, and not at startup.

If you don't have fuel/spark, check the two sensors on the bellhousing. Make sure they are properly connected.

If those quick tests don't reveal an obvious problem, it's time to get out the volt meter, fuel pressure gauge, and Bentley manual, and start checking everything.

[REIMER]

You all are awesome! Thanks for all the help. And yea the actual sensor didn't fall out it got unplugged from catching something on the ground and I replaced it because the wires where shredded.
I will start with this stuff. Hopefully it's something simple.

[Andy.B]

You all are awesome! Thanks for all the help. And yea the actual sensor didn't fall out it got unplugged from catching something on the ground and I replaced it because the wires where shredded.
I will start with this stuff. Hopefully it's something simple.

OK. I have a long shot theory. On ETA's, the o2 sensor essentially had an extension cord that runs from the sensor up to the engine compartment next to the exhaust manifold by the firewall. I would find that connector (the main engine harness to the o2 sensor extension harness) and unplug it, then try to start the car again. I wonder if the cable got damaged somewhere, and is shorting out.

[uturn]

On my first e30 the magnet on the flywheel that the cps picks up on fell out. That caused a no start condition for me. I was lucky, that little guy stuck around in the bell housing and I was able to tap him back in.